ionic: missed doorbell workaround

In one version of the HW there is a remote possibility that it
will miss the doorbell ring.  This adds a bit of protection to
be sure we don't stall a queue from a missed doorbell.

Fixes: 0f3154e6bcb3 ("ionic: Add Tx and Rx handling")
Signed-off-by: Allen Hubbe <allen.hubbe@amd.com>
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 85 insertions, 2 deletions

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
index 0c3977416cd1..f761780f0162 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
@@ -22,6 +22,67 @@ static inline void ionic_rxq_post(struct ionic_queue *q, bool ring_dbell,
 	ionic_q_post(q, ring_dbell, cb_func, cb_arg);
 }
 
+bool ionic_txq_poke_doorbell(struct ionic_queue *q)
+{
+	unsigned long now, then, dif;
+	struct netdev_queue *netdev_txq;
+	struct net_device *netdev;
+
+	netdev = q->lif->netdev;
+	netdev_txq = netdev_get_tx_queue(netdev, q->index);
+
+	HARD_TX_LOCK(netdev, netdev_txq, smp_processor_id());
+
+	if (q->tail_idx == q->head_idx) {
+		HARD_TX_UNLOCK(netdev, netdev_txq);
+		return false;
+	}
+
+	now = READ_ONCE(jiffies);
+	then = q->dbell_jiffies;
+	dif = now - then;
+
+	if (dif > q->dbell_deadline) {
+		ionic_dbell_ring(q->lif->kern_dbpage, q->hw_type,
+				 q->dbval | q->head_idx);
+
+		q->dbell_jiffies = now;
+	}
+
+	HARD_TX_UNLOCK(netdev, netdev_txq);
+
+	return true;
+}
+
+bool ionic_rxq_poke_doorbell(struct ionic_queue *q)
+{
+	unsigned long now, then, dif;
+
+	/* no lock, called from rx napi or txrx napi, nothing else can fill */
+
+	if (q->tail_idx == q->head_idx)
+		return false;
+
+	now = READ_ONCE(jiffies);
+	then = q->dbell_jiffies;
+	dif = now - then;
+
+	if (dif > q->dbell_deadline) {
+		ionic_dbell_ring(q->lif->kern_dbpage, q->hw_type,
+				 q->dbval | q->head_idx);
+
+		q->dbell_jiffies = now;
+
+		dif = 2 * q->dbell_deadline;
+		if (dif > IONIC_RX_MAX_DOORBELL_DEADLINE)
+			dif = IONIC_RX_MAX_DOORBELL_DEADLINE;
+
+		q->dbell_deadline = dif;
+	}
+
+	return true;
+}
+
 static inline struct netdev_queue *q_to_ndq(struct ionic_queue *q)
 {
 	return netdev_get_tx_queue(q->lif->netdev, q->index);
@@ -424,6 +485,12 @@ void ionic_rx_fill(struct ionic_queue *q)
 
 	ionic_dbell_ring(q->lif->kern_dbpage, q->hw_type,
 			 q->dbval | q->head_idx);
+
+	q->dbell_deadline = IONIC_RX_MIN_DOORBELL_DEADLINE;
+	q->dbell_jiffies = jiffies;
+
+	mod_timer(&q_to_qcq(q)->napi_qcq->napi_deadline,
+		  jiffies + IONIC_NAPI_DEADLINE);
 }
 
 void ionic_rx_empty(struct ionic_queue *q)
@@ -511,6 +578,9 @@ int ionic_tx_napi(struct napi_struct *napi, int budget)
 				   work_done, flags);
 	}
 
+	if (!work_done && ionic_txq_poke_doorbell(&qcq->q))
+		mod_timer(&qcq->napi_deadline, jiffies + IONIC_NAPI_DEADLINE);
+
 	return work_done;
 }
 
@@ -544,23 +614,29 @@ int ionic_rx_napi(struct napi_struct *napi, int budget)
 				   work_done, flags);
 	}
 
+	if (!work_done && ionic_rxq_poke_doorbell(&qcq->q))
+		mod_timer(&qcq->napi_deadline, jiffies + IONIC_NAPI_DEADLINE);
+
 	return work_done;
 }
 
 int ionic_txrx_napi(struct napi_struct *napi, int budget)
 {
-	struct ionic_qcq *qcq = napi_to_qcq(napi);
+	struct ionic_qcq *rxqcq = napi_to_qcq(napi);
 	struct ionic_cq *rxcq = napi_to_cq(napi);
 	unsigned int qi = rxcq->bound_q->index;
+	struct ionic_qcq *txqcq;
 	struct ionic_dev *idev;
 	struct ionic_lif *lif;
 	struct ionic_cq *txcq;
+	bool resched = false;
 	u32 rx_work_done = 0;
 	u32 tx_work_done = 0;
 	u32 flags = 0;
 
 	lif = rxcq->bound_q->lif;
 	idev = &lif->ionic->idev;
+	txqcq = lif->txqcqs[qi];
 	txcq = &lif->txqcqs[qi]->cq;
 
 	tx_work_done = ionic_cq_service(txcq, IONIC_TX_BUDGET_DEFAULT,
@@ -572,7 +648,7 @@ int ionic_txrx_napi(struct napi_struct *napi, int budget)
 	ionic_rx_fill(rxcq->bound_q);
 
 	if (rx_work_done < budget && napi_complete_done(napi, rx_work_done)) {
-		ionic_dim_update(qcq, 0);
+		ionic_dim_update(rxqcq, 0);
 		flags |= IONIC_INTR_CRED_UNMASK;
 		rxcq->bound_intr->rearm_count++;
 	}
@@ -583,6 +659,13 @@ int ionic_txrx_napi(struct napi_struct *napi, int budget)
 				   tx_work_done + rx_work_done, flags);
 	}
 
+	if (!rx_work_done && ionic_rxq_poke_doorbell(&rxqcq->q))
+		resched = true;
+	if (!tx_work_done && ionic_txq_poke_doorbell(&txqcq->q))
+		resched = true;
+	if (resched)
+		mod_timer(&rxqcq->napi_deadline, jiffies + IONIC_NAPI_DEADLINE);
+
 	return rx_work_done;
 }